生物可降解塑料的发酵生产研究进展*

近十几年来,随着化学合成塑料造成环境污染的日趋严重,微生物合成生物可降解塑料的研究受到人们的广泛重视.聚羟基烷酸(polyhydroxyalkanoates,PHA)具有与化学合成塑料相似的性质,能拉丝、压模、注塑等,而且具有合成塑料所没有的特殊性能,如利用其生物相容性可作为外科手术缝线、人造血管和骨骼代用品,术后无需取出.因而在工业、农业、医药和环保等行业都具有广阔的应用前景.     

新型生物可降解塑料——多聚羟基烷酸研究进展

面对日益严重的白色污染 ,人们迫切需要一种能在自然界较快分解的新型塑料。多聚羟基烷酸是原核生物在不平衡代谢条件下形成的碳源和能源贮藏物质 ,这种贮藏物质如同淀粉、糖原一样 ,当生命活动需要时可以再分解利用。由于多聚羟基烷酸有着与石化塑料相似的理化性质 ,又能在一定条件下被微生物迅速而彻底地降解 ,因此是一种理想的传统石化塑料替代品。1　多聚羟基烷酸的理化及生物学特性1 1　多聚羟基烷酸的分子结构及理化性质多聚羟基烷酸是由羟基脂肪酸单体首尾相联构成的高分图 1　多聚羟基烷酸的分子结构子聚合物。又分为不同种类。如多…     

生物技术生产生物可降解塑料PHB的研究进展

本文综述了ＰＨＢ的合成和降解途径及其关键酶的基因克隆,比较了细菌发酵法及遗传吃力菌生产ＰＨＢ的优缺点并讨论了发酵法生产及ＰＨＡｓ的前景。随着近年来植物基因工程的发展,用植物大规模生产生物可降解塑料已成为可能,但然后存在许多障碍,本文进一步探讨了转基因植物生产ＰＨＢ的限制因素和克服方法。     

微生物发酵聚羟基烷酸（PHA）研究进展

聚羟基烷酸是一类生物可降解塑料,具有良好的应用前景,正成为全世界关注的研究热点,它是许多微生物在Ｃ,Ｎ源失衡条件下作为胞内碳源和能源储存物而大量积累产生的。本文着重对国内外微生物发酵ＰＨＡ研究水平和培养方法进行了简要介绍,并对发展方向作了探讨。     

流加发酵法生产生物可降解多聚体

聚羟基烷酸（ＰＨＡｓ）是微生物细胞在其营养不平衡的生长条件下积累的一类胞内聚酯。由于ＰＨＡｓ具有生物可降解性和生物可相容性,因而被认为是替代化学合成塑料最具潜力的多聚体,已受到广泛的重视。目前ＰＨＡｓ中研究和应用的最多的是聚β－羟基丁酸（ＰＨＢ）和３－羟基丁酸与３－羟基戊酸的共聚物Ｐ（ＨＢ－ｃｏ－ＨＶ）。流加发酵技术是提高聚合物生产速率和改进其质量的关键,具体表现在采用Ｐｓｅｕｄｏｍｏｎａｓｓｐ．ｋ和Ａｌｃａｌｉｇｅｎｅｓｅｕｔｒｏｐｈｕｓ,在适宜的流加培养条件下,可达到聚合物在细胞内的最大积累、控制共聚物适宜的聚合分率和得到平均分子量大且分布范围窄的产物。因此针对于某种特定的微生物,研究得到生物可降解多聚体的一套最佳流加培养策略至关重要。     

微生物合成可降解塑料聚羟基链烷酸（PHA）

本文综述利用微生物合成主要包括聚羟基丁酸（ＰＨＢ）和聚羟基丁酸－羟基戊酸（ＰＨＢＶ）在内的聚羟基链烷酸的若干要素,如微生物种资源、生物合成途径、发酵以及产物的性质和应用。     

生物技术生产生物可降解塑料PHB的前景

生物技术生产生物可降解塑料ＰＨＢ的前景谢安勇,宋艳茹（中国科学院植物研究所,北京１０００４４）ＰＲＯＳＰＥＣＴＯＦＰＲＯＣＵＣＩＮＧＰＨＢ,ＡＢＩＯＤＥＧＲＡＤＡＢＬＥＰＬＡＳＴＩＣＢＹＵＳＩＮＧＢＩＯＴＢＣＨＮＯＬＯＧＹ￥ＸｉｅＡｎ－ｙｏｎｇ;Ｓｏ...     

生物可降解塑料——人类消除白色污染的希望

随着塑料工业的发展,各行各业对塑料制品的需求越来越大,从而使塑料的消耗逐年增加,近年来废弃塑料对环境造成的污染也日趋严重:包括对野生动植物的影响;对城市、森林景观的破坏;可利用土地的减少等。人们逐渐认识到,过去对工业及日常使用的塑料制品所要求的持久性、耐降解性,如今却成了消除“白色污染”的难题。     

生物可降解塑料单体二元羧酸的生物合成研究进展北大核心CSCD

塑料是最重要的聚合物材料之一,需求量巨大,但存在处理困难、污染大等缺点。环境友好型的生物可降解塑料有望成为目前塑料的替代品,以满足社会各界对于塑料制品日益增长的需求。二元羧酸是生物可降解塑料中重要的单体之一,可降解性强,应用广泛,并且可以通过全生物法合成。因此,本文重点选取了几种比较有代表性的二元羧酸,总结它们的生物合成途径以及其代谢改造手段,以期为中长链等复杂二元羧酸的生物法合成提供借鉴。     

利用蓝细菌生产可降解塑料

德国蒂宾根大学的研究人员在最近的Microbial Cell Factories和PNAS上发表的几项研究中,介绍了他们成功地改变了蓝细菌的代谢通路,生产出了具有良好生物降解特性的有前途的生物塑料替代品——PHB。该方法有望在工业上大量使用,与对环境有害的石油基塑料竞争。蓝细菌,又称微藻或蓝藻,是地球上最不起眼但功能最强大的细菌之一。     

Fermentative Production of l-Arginine

Most of the bacteria, which were examined for the sensitivity to l-arginine analogs (l-canavanine, l-homoarginine, d-arginine and arginine hydroxamate), were insensitive to the analogs at a concentration of 8 mg/ml. Corynebacterium glutamicum DSS-8 isolated as d-serine-sensitive mutant from an isoleucine auxotroph KY 10150, was found to be sensitive to d-arginine and arginine hydroxamate. Furthermore, DSS-8 produced l-arginine in a cultural medium. l-Arginine analog-resistant mutants were derived from DSS-8 by N-methyl-N′-nitro-N-nitrosoguanidine (NTG) treatment. Most of them were found to produce a large amount of l-arginine. An isoleucine revertant from one of these mutants produced 19.6 mg/ml of l-arginine in the medium containing 15% (as sugar) of molasses.

The mechanism of the sensitivity to l-arginine analogs and that of the production of l-arginine in the d-serine-sensitive mutant, DSS-8, were investigated. DSS-8 seems to be a mutant having increased permeability to d- and l-arginine.     

Fermentative Production of Piperazinium Dilactate

In order to test whether piperazinium dilactate can be produced by fermentation in its exact stoichiometric composition without losses of yield, the kinetics of cell growth and lactate production were investigated in the batch cultivation of Lactobacillus paracasei, using piperazine as a neutralizer in pH control. It was found that piperazine dilactate is formed in its stoichiometric composition at about pH 5.0, and lactic acid fermentation occurred with yields of about 90% under these conditions. Piperazine at concentrations less than or equal to 50 g/l did not affect growth and product formation. The presence or absence of piperazine did not produce any significant differences in either the maximum specific growth rate or the maximum specific lactate formation rate when piperazine was present or absent (0.65 h^—1 compared to 0.68 h^—1 and 3.86 g/g × h compared to 3.63 g/g × h, respectively). The Luedeking‐Piuret relationship between the two quantities was also not changed significantly when piperazine was added. To estimate the optimum parameters for cell growth and lactate formation in the presence of piperazine, a factorial experiment was designed and carried out under consideration of the parameter ranges 5.0 ≤ pH ≤ 7.0 and 30 °C ≤ T ≤ 36 °C. In this way, three‐dimensional models of the specific growth rate, the specific lactate formation rate and the lactate yield were obtained.     

Fermentative Production of CDP-Choline by Yeasts

The optimum condition for the formation of CDP-choline was studied: (1) the reaction proceeded more effectively at 35°C than at 28 or 40°C. (2) the maximum formation of CDP-choline was obtained at pH 7.5, when pH levels were kept constant throughout the reaction. (3) twenty #x03BC;moles per ml of 5′-CMP was the optimum concentration for the formation of CDP-choline. When higher concentration of 5′-CMP was employed, the substrate was decomposed to uridine, uracil, etc., and the yield of CDP-choline decreased. By the application of feeding method, 5′-CMP was utilized to the effective formation of CDP-choline without further formation of side-products.     

微生物发酵产氢的影响因素分析*

随着环保要求的愈益严格和化石能源的日益短缺,氢作为清洁高效的可再生能源日益受到人们的重视。微生物发酵产氢可以利用可再生的生物质,符合可持续发展的要求。针对影响微生物发酵产氢的因素,总结了国内外在该领域的研究成果,重点介绍了产氢微生物、营养物、产物和工艺操作条件等方面对发酵产氢的影响,同时还阐述了以有机废弃物为基质时的发酵产氢影响因素。     

Production of Nucleic Acid-Related Substances by Fermentative Processes

The inhibitory effects of 20 compounds including purine analogues on the growth of Micrococcus glutamicus No. 534–348, an inosinic acid-producing adenine-auxotroph, and No. 534, a prototrophic strain, were investigated.

A number of strains resistant to each of 6-merca ptoguanine, 6-thioguanine, 8-azaguanine, mitomycin C and sulfanilamide were induced from strain No. 534–348, and their inosinic acid productivities were compared with their parent strain. Among them, MGR-25, α 6-mercaptoguanine-resistant strain, accumulated more inosinic acid than its parent strain. Furthermore, the strain MGR-25 was differentiated in its morphology, frequency of spontaneous reversion to prototrophic type in adenine-deficient medium, and the effectiveness of hypoxanthine to increase the inosinic acid accumulation.     

Production of Nucleic Acid-Related Substances by Fermentative Processes

An adenine-requiring mutant (KY7208) of Brevibacterium ammoniagenes ATTC 6872 was found to accumulate an appreciable quantity of IMP and hypoxanthine in the culture liquid.

Crystalline IMP was isolated from culture broth of KY7208 by the use of ion-exchange columns. The preparation obtained was definitely identified as 5′-IMP, based on the results on paperchromatography, UV and IR absorption spectra, and analyses of its hydrolysates.

Growth responses of this mutant were demonstrated to adenine and adenosine, but not to 5′-AMP, 3′-AMP and 5′-AMP.

Over 5 mg of IMP per ml of broth were produced by the organism in natural medium consisting of glucose, yeast extract, urea, high concentrations of phosphate and magnesim salts, and others. The chemical changes showed that hypoxanthine first accumulated in the earlier stage of fermentation, and IMP synthesis then took place with the disappearance of hypoxanthine in the later stage of fermentation.